Agent for polishing, sharpening, and grinding articles of great hardness



Patented Dec. 18, 1934 PATENT OFFICE AGENT FOR POLISHING, SHZLBPENING,AND

GRINDING ARTICLES OF GREAT HARD- NESS Reinhold Ieeiclunan'n, Berlin,Germany, I

to Siemens & m tion oi Germany aligns! Halske, Aktiengesellschalt. Siet,near Berlin, Germany, a m- No Drawing. Application May 25, 1933, SerialGermany No. 672,808. In

May 30, 1932 4 Claims. (C1. 51-219) My invention relates to an agent forpolishing, sharpening and grinding articles of great hardness,particularly hard alloys.

Silicon carbide belongs to the class of the 5 hardest grinding materialsextensively in use. It is employed, particularly in grinding theso-called hard alloys and metallic carbides which are known in themarket under various names. The good grinding eilect as a result of thegreat hardness of the silicon carbide is, however, im-

paired due to the fact that the crystals are united by means of anargillaceous binding agent, the strength or which is very slight ascompared to the strength of the crystals. The crystals are easily pulledapart when machining very hard materials, and the structure is subjectedto deterioration, thus causing not only a considerable wear of thegrindstones but also reducing the grinding emciency to a minimum.

The object of my present invention is, therefore, to employ as polishingand grinding agent for articles of great hardness the purest possibleberyllium oxide sintered at a temperature above 1700 C. l Berylliumoxide has hitherto been employed chiefly in the manufacture ofrefractory crucibles. However, its adaptability as polishing andgrinding agent for articles 0! great hardness has not been recognisedheretofore. The use oi beryllium oxide in the iorm oi solid bodies suchas grindstones and the like is of particular advantage. In this case theparticles of the beryllium'oxidemaybeunitedbyamaterialwhichisalsosintered at a high temperature, such asaluminium oxide. However, a still-more compact structure is attained itonly the pure particles 0! beryllium oxide are shaped, for instance withthe aid of .1700 C., for instance,

a moldable slip or by pressing and if the resulting bodies are sinteredat a temperature above between 1900' C. and is continued 2000 C. II thesintering process for a sumciently long time at a high temperature thebody is considerably. solidified by the coalescence oi the crystals.

The bodies obtained in the above described manner may not only beutilized for grinding hard metallic alloys and similar materials butthey also lend themselves to the grinding and polishing of articlesconsisting of sintered metallic oxides, for instance, highly sinteredaluminium oxide, which owing to itsgreat hardness,

could hardly be machined in the past. The agent,

however, may also be utilised in a pulverized form.

I claim: '1. An agent for polishing, sharpening and purity.

RIINHOLD an abrasive body of

